JP2002116604A - Surface plane for electrification and plate making system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the change of potential in spike shape from occurring on an electrified printing plate when a notch reaching the periphery part of the printing plate is formed on a surface plane for plotting. SOLUTION: In the case of forming the notch 154 reaching the periphery part of the printing plate 12 at the end in the moving direction of the plotting surface plane 22, a numerical aperture Q being the ratio of the total sum Ws of the width dimension Wd of the notch to the width dimension WD of the plotting surface plane is set to be <=75% when the notch is formed at one spot or dispersed to plural spots in a width direction orthogonal to the moving direction of the plotting surface plane. Thus, the potential at the end in the moving direction of the printing plate is prevented from rising in the spike shape when exposure is performed by moving the plotting surface plane relatively to an electrifier while controlling the current of a high voltage power source for discharge, and all the surface of the printing plate is electrified so that its potential may be uniform.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging surface plate for charging a photoconductor by mounting a photoconductor which forms an electrostatic latent image by exposure and moving relative to a charger. It relates to a plate making system.

[0002]

2. Description of the Related Art A photosensitive lithographic printing plate used for newspaper printing includes an OPC printing plate (hereinafter, referred to as a "printing plate") using an organic photoconductor for a photosensitive layer formed on an aluminum support. is there. In a plate making system using this printing plate, the photosensitive layer of the printing plate is uniformly charged, and then the image is directly recorded by scanning and exposing with a laser beam or the like. Thereafter, by supplying a liquid developer containing toner particles to the surface of the printing plate, the toner particles are adhered and fixed in accordance with the electrostatic latent image to form a blocking layer. The elution results in a printing plate. As described above, a printing plate having a photosensitive layer formed using an organic photoconductor can be manufactured without using a document film or the like.

In the drawing section of the photomechanical system, the printing plate is positioned and placed on a metal surface plate, and the photosensitive layer of the printing plate is uniformly charged by a charger and then irradiated with laser light or the like. The printing plate is scanned and exposed to form an electrostatic latent image.

A charging device used for charging a printing plate is such that a thin wire is arranged in a shield having an open surface facing the printing plate placed on the platen, and the platen on which the printing plate is placed is a wire. A corona discharge is generated by applying a high voltage to the wire when moving at a position facing the wire. By radiating the charges generated by the corona discharge toward the surface plate, a charging current flows, and the printing plate on the surface plate is charged according to the charging current.

For controlling the charger, a voltage control method for controlling the voltage of the wire to be constant or a current control method for controlling the current flowing through the wire to be constant are used.

On the other hand, in order to uniformly charge the printing plate, it is necessary to keep the current flowing through the printing plate constant. For this reason, a shield feedback current control method has been proposed (for example, Japanese Patent Laid-Open No. 5-158288). Gazette). In this shield feedback current control method, the charging current is made constant by controlling the shield current so that the entire surface of the photosensitive layer of the printing plate is charged to a constant potential.

By the way, when the printing plate is taken out from the surface plate, if the suction cup or the like is brought into contact with the surface of the printing plate on which the electrostatic latent image is formed, the electrostatic latent image disappears. For this purpose, cuts are formed at a plurality of locations on the surface plate facing the peripheral edge of the printing plate,
The lower surface of the printing plate is supported by the claws inserted into the cuts, and the printing plate is lifted from the surface plate and taken out.

[0008]

However, if a notch reaching the peripheral portion of the printing plate is formed on the surface plate, the potential of the peripheral portion of the charged printing plate becomes spike-like. This increase in the potential on the spikes damages the photosensitive layer of the printing plate and appears as black spots, etc., and deteriorates the image formed on the printing plate and the finished quality of the printed matter printed using this printing plate. Problem arises.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and it has been made possible to take out a photoconductor without bringing a suction cup or the like into contact with the surface of a plate-shaped photoconductor such as a printing plate. It is proposed to propose a charging platen and a plate making system that enables stable charging of the photoconductor when a notch or the like reaching the peripheral portion of the placed photoconductor is formed in order to perform positioning. Aim.

[0010]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention comprises a discharge wire disposed in a shield having one open side, and a current control supplied from a high voltage power supply for discharge. When a photoconductor is placed on a flat upper surface, and the photoconductor passes through a position facing the wire, the photoconductor is discharged by the wire. The charging platen to be charged, when forming a notch reaching the peripheral edge of the photoconductor at the end of the flat plate along the direction of relative movement with the wire, the relative movement direction of the flat plate and An opening ratio, which is a ratio of a total sum of opening widths of the cuts in a direction orthogonal to the relative movement direction with respect to a board size in the orthogonal direction, is 75% or less.

The charging platen of the present invention uses a charger for charging a plate-shaped photoconductor such as a printing plate by discharging a wire surrounded by a shield. Are relatively moved along a direction orthogonal to. At this time, by controlling the current supplied from the high voltage power source for discharging, the entire surface of the printing plate is uniformly charged.

Further, the charging platen of the present invention forms a notch reaching the peripheral portion of the placed photoconductor, thereby positioning the photoconductor and forming a suction cup on the upper surface of the charged photoconductor. Etc. can be taken out without contact.

On the other hand, in the charging step, when the photoconductor is placed on a flat plate, a high voltage is applied to the wires of the charger from a high voltage power source for discharging. In this state, the photoconductor is uniformly charged by moving the flat plate on which the photoconductor is mounted at a constant speed. After the flat plate has passed through the charger, the application of the high voltage is stopped, and the charging is terminated.

Here, for example, when it is attempted to uniformly charge the photoconductor by controlling the shield return current, the flat plate on which the photoconductor is placed does not face the charger, and the state before the start of charging is set. , Because there is no charging current returning from the flat plate,
The corona current supplied to the wire increases and the voltage applied to the wire increases. Next, the movement of the flat plate is started, and when the flat plate on which the photoconductor is placed faces the charger, the return current from the flat plate increases, so that the corona current supplied to the wire is reduced. The voltage applied to is reduced.

As described above, in the charger, by controlling the shield return current, when the photoconductor opposes the wire, the charging current becomes substantially constant, and the photoconductor is brought to a predetermined potential. It is made to be charged.

Here, when a notch reaching the periphery of the photoconductor is formed at an end of the flat photoconductor along the direction of relative movement, if the opening of the notch is large, the photoconductor will not move. When the ends pass, the change in the charging current is large, which increases the potential at the ends of the photoconductor.

At this time, in the present invention, by limiting the total opening width due to the cut, the change in the charging voltage when the end of the photoconductor passes the position facing the charger is suppressed, and The body is charged to a substantially uniform potential. That is, when the end of the photoconductor in the moving direction passes through a position facing the charger, the opening is restricted so as to prevent a change in the potential of the photoconductor from occurring. Of the photosensitive layer can be prevented from being partially (spike-shaped), and the photosensitive layer can be prevented from being damaged due to the partially increased potential.

According to the present invention, there is provided a closing means for closing a part of the opening formed on the upper surface by the cut so that the total of the opening widths is not more than a predetermined value at least when the printing plate is charged. be able to.

Further, in the present invention, the distance between the end of the flat plate and the end of the photoconductor along the relative movement direction is 15 minutes.
mm or more, more preferably 30 mm or more.

The plate making system of the present invention is a plate making system for forming a printing plate by forming an image on a printing plate using a photoconductor by charging and exposing the charged plate, wherein the printing plate is charged. An image exposure unit for performing image exposure later is provided with the drawing surface plate according to any one of claims 1 to 3.

In the plate making system of the present invention, since the photoconductive member can be charged substantially uniformly by providing the charging surface plate having the above-mentioned structure, the electrostatic latent surface formed on the photoconductive member can be formed. It is possible to form a high-quality image without deteriorating the image quality due to damage to the image or the like. For example, it is possible to create a printing plate capable of obtaining a printed matter having a high finish quality.

[0022]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of a plate making system 10 applied to the present embodiment.

The plate-making system 10 is a so-called O-plate in which a conductive, thin rectangular aluminum plate is used as a support, and a photosensitive layer is formed on one surface of the support using an organic photoconductor.
Using a PC printing plate (hereinafter, referred to as “printing plate 12”), a printing plate that can be mounted on a printing rotary press (not shown) is created through predetermined processing steps such as charging exposure and wet development. As the printing plate 12, a size in which images of one page of newspaper are arranged vertically (about 400 mm × about 1100 mm) or a size in which images of one spread of newspaper (two pages of newspaper horizontal) are arranged vertically ( About 800
mm × about 1100 mm).

The printing plate 12 is mounted on a mounting table (skid 1).
In 4), transportation and storage are performed in a state in which a large number of sheets (for example, about 500 to 1000 sheets) are stacked with the photosensitive layer facing downward.

The plate making system 10 is provided with a plate feeding / discharging device 16, and a skid 14 on which the printing plate 12 is mounted is loaded into the plate feeding / discharging device 16. The plate making system 10 includes an exposure unit 1 adjacent to the plate feeding / discharging device 16.
8 is provided. The printing plate 12 is loaded into the plate supply / discharge device 16 such that the longitudinal direction is the direction of the arrow L in FIG. 1 and the direction (width direction) orthogonal to the longitudinal direction is the direction of the arrow W in FIG.

The plate feeding / discharging device 16 takes out the printing plates 12 stacked on the skid 14 one by one from the uppermost layer, and turns the photosensitive layers upward by transporting them along the width direction of the printing plates 12 and inverting them. Then, it is placed on the drawing surface plate 22 of the drawing device 20.

After positioning the printing plate 12 on the drawing surface plate 22, the drawing device 20 moves the printing plate 12 toward the exposure unit 18. At this time, after uniformly charging the photosensitive layer of the printing plate 12 that moves together with the drawing platen 22, the exposure unit 18 irradiates the printing plate 12 with a light beam such as a laser beam according to image data. The plate 12 is exposed to form an electrostatic latent image on the printing plate 12 according to the image data. The drawing device 20 charges, for example, the photosensitive layer of the printing plate 12 to a positive value, and the exposure unit 18 removes the charge of the corresponding portion by exposing a portion that becomes an image during printing.

The plate making system 10 includes a developing / fixing device 28 provided with a developing unit 24 and a fixing unit 26 from the plate feeding / discharging device 16 along the direction of arrow L, an eluting device 32 provided with an eluting unit 30, and a drying unit 34. Are provided continuously. When the image exposure is completed, the printing plate 12 is conveyed in the width direction and returned to the plate supply / discharge device 16,
The sheet is fed from the plate feeding / discharging device 16 to the developing section 24 of the developing / fixing device 28 while being inclined at a predetermined angle.

In the developing section 24, a liquid developer containing toner particles is supplied to the upper surface (surface on the photosensitive layer side) of the printing plate 12 which is fed at a predetermined angle and is exposed to light (an electrostatic latent image). The toner particles are adhered (exposed image portions) in accordance with (1) and sent to the fixing unit 26.

In the fixing section 26, the toner particles adhering to the printing plate 12 are melted and fixed (fixed) by heating to form a blocking layer at the time of elution. To elute (etch) the photosensitive layer on which the toner particles are not adhered, and then apply a gum solution for protecting the plate surface. Drying section 34
Then, the gum solution applied to the printing plate 12 is dried to form a protective film and sent to the standby unit 38.

The standby portion 38 is provided with a punch / plate bending device 44 having a punch portion 40 and a plate bending portion 42 on one side of the printing plate 12 in the width direction. The printing plate 12 is conveyed from the standby unit 38 in the width direction at a predetermined timing and sent to the punch unit 40.

In the punch section 40, a notch or a punch hole is formed at a predetermined position at an end in the longitudinal direction of the printing plate 12 which is the top and bottom direction of the image formed on the printing plate 12, and the plate bending section 4 is formed.
Send to 2. In the plate bending section 42, a bending process (plate bending process) for mounting the printing plate 12 on a plate cylinder of a rotary press for printing is performed on both ends in the longitudinal direction of the printing plate 12 based on the punch holes or cutouts. Discharge. The printing plates 12 for which the plate bending process has been completed are sequentially accumulated in, for example, a stocker (not shown) and transported to a printing process.

As shown in FIG. 2 and FIG.
6, a plate feeding section 46 is provided below the plate feeding section 46.
Is provided above the plate. The skid 14 on which the printing plate 12 is mounted is positioned and loaded at a predetermined position of the plate feeding section 46. The inside of the plate supply / discharge device 16 and the drawing device 20 is shielded from light so that the printing plate 12 is not unnecessarily exposed.

As shown in FIG. 2, the plate supply / discharge device 16 includes:
Suction removal unit 102 and reverse transport unit 104
Is provided. The suction take-out unit 102 stands by above the loaded skid 14, and the reverse transport unit 104 stands by adjacent to the suction take-out unit 102.

The suction take-out unit 102 sucks and lifts the printing plate 12 on the outermost surface of the skid 14 by a plurality of suction cups 106 to sequentially take out the printing plate 12. At this time, the printing plate 12
Since the photosensitive surface is directed downward and the surface of the support opposite to the photosensitive surface is adsorbed by the suction cup 106, no trace of adsorption of the suction cup 106 or the like appears on the photosensitive surface.

The reverse transport unit 104 has a plurality of suction cups 110 provided on a shaft 108 arranged along the longitudinal direction of the printing plate 12. These suckers 110
The suction take-out unit 102 is opposed along one end in the width direction of the printing plate 12 lifted by suction, and the suction take-out unit 102 suction-holds one end in the width direction of the printing plate 12 lifted. As a result, the reverse transport unit 104 receives the printing plate 12 from the suction take-out unit 102.

Upon receiving the printing plate 12, the reverse transport unit 104 holds the printing plate 12 in a cantilevered state and moves toward the drawing device 20. At this time, the reversing transport unit 104 reverses the printing plate 12 by rotating the shaft 108, and turns the photosensitive surface, which has been directed downward, upward. In the subsequent steps, the printing plate 12 is conveyed with the photosensitive surface facing upward.

The plate feeding section 46 is provided with a lift table 112 on the drawing apparatus 20 side. The lift table 112 rises in synchronization with the transport and reversal operation of the printing plate 12 by the reversing transport unit 104, and is mounted so as to scoop up the end of the reversed printing plate 12, and
Receive from 04.

At the highest position of the lift table 112, a horizontal transfer unit 114 is provided so as to face the lift table 112. The plate feeding unit 46 is provided with a positioning means (not shown). Before the lift table 112 reaches the highest position, the lifting is stopped at a position facing the positioning means, and the printing plate 12 is moved in width. The printing plate 12 is positioned with respect to the lift table 112 by pressing and moving along the direction and the longitudinal direction. Thereby, the printing plate 12
Are positioned with respect to the horizontal transport unit 114.

The horizontal transfer unit 114 includes the lift table 11
2 is provided with a plurality of claws 116 opposed to the periphery of the printing plate 12 positioned at 2. When the lift base 112 reaches the highest position and stops, the tip of each claw 116 is moved to the periphery of the printing plate 12. Insert below the part. By lowering the lift table 112 toward the standby position in this state, the printing plate 12 is supported by the claw portions 116 and taken out of the lift table 112.

The horizontal transport unit 114 is provided with a printing plate 12 by horizontal moving means (not shown) such as a rodless cylinder.
The plurality of claw portions 116 are integrally formed while the
Move horizontally into 0. As a result, the printing plate 12 supported by the claws 116 is sent into the drawing device 20.

As described above, the drawing surface plate 22 is provided in the drawing device 20 and the horizontal transport unit 114 is provided.
When the printing plate 12 reaches a predetermined position above the drawing platen 22, the claw portion 116 is retracted from below the peripheral portion of the printing plate 12. Thereby, the printing plate 12 falls on the drawing surface plate 22 and is placed on the drawing surface plate 22.

FIG. 4 shows a schematic configuration of the drawing apparatus 20. The drawing device 20 is provided with a frame 120 that is long along the longitudinal direction of the printing plate 12. Drawing surface plate 22
Are arranged on the frame 120. In addition, frame stand 1
A moving table 122 is provided at 20, and the drawing surface plate 22 is mounted on the moving table 122.

The moving table 122 is movably attached to a pair of guide rails 124 arranged on the frame table 120. The guide rail 124 has a longitudinal direction arranged along the longitudinal direction of the printing plate 12, and the moving table 122 is movable along the guide rail 124. A moving mechanism 12 composed of, for example, a feed screw and a feed nut is provided between the frame base 120 and the moving base 122.
6 are provided.

Thus, the moving table 122 is moved by the moving mechanism 1
By the operation of 26, the printing plate 12 is moved along the longitudinal direction of the printing plate 12 together with the drawing platen 22 on which the printing plate 12 is placed.

In the drawing apparatus 20, one end of the guide rail 124 is a position for receiving and taking out the printing plate 12, and an exposure unit 18 is provided on the other end. Further, a charger 130 is provided on the front side of the exposure unit 18 (on the side where the printing plate 12 is received and taken out).

When the printing plate 12 is placed on the drawing platen 22, the drawing device 20 operates the moving mechanism 126 to move the drawing platen 22 toward the exposure unit 18. Thus, the printing plate 12 passes below the charger 130 and is sent below the exposure unit 18 while moving at a predetermined speed. At this time, the charger 130 charges the photosensitive layer of the printing plate 12 by corona discharge.

When the charging of the printing plate 121 is completed, the moving mechanism 126 rotates in the reverse direction, and is pulled out from below the exposure unit 18. At this time, the exposure unit 18 scans and exposes the printing plate 12 based on the image data,
An electrostatic latent image is formed on the printing plate 12. That is, the charged printing plate 12 is irradiated with the light beam, so that the charge in the region irradiated with the light beam is removed, and the developing unit 2
At 4, an image portion to which the toner particles adhere is formed.

As shown in FIG. 2, above the drawing surface plate 22 returned to the take-out position, a take-out unit 132 is on standby. The take-out unit 132 is used for the printing plate 12
Are provided with a plurality of claw portions 134 facing the peripheral edge portion. The plurality of claw portions 134 are integrally moved up and down by elevating means such as an air cylinder 136, and are horizontally movable integrally toward the plate discharging section 48 by horizontal moving means (not shown) such as a rodless cylinder. .

When the printing plate 12 after the image exposure is returned to the take-out position, the take-out unit 132 drives the air cylinder 136 to move the claw portions 134 downward, and then prints the tips of the claw portions 134. The plate 12 is inserted below the periphery. In this state, by moving the claw portion 134 upward integrally, the printing plate 12 causes the peripheral portion to move to the plurality of claw portions 134.
And lifted out of the drawing surface plate 22 and taken out. Further, when the printing plate 12 is lifted, the take-out unit 132 uses the horizontal moving means (not shown) to move the printing plate
Move horizontally to 8 side.

The plate discharging section 48 is provided with a transport stage 138 which can protrude into the drawing apparatus 20 by moving horizontally. The transport stage 138 is horizontally moved into the drawing device 20 and inserted below the printing plate 12 in synchronization with the horizontal movement of the printing plate 12 by the take-out unit 132. In this state, by retracting the tip of the claw portion 134 from below the peripheral surface of the printing plate 12, the printing plate 12 is dropped and mounted on the transport stage 138.

As shown in FIGS. 2 and 3, the plate discharging section 48 is provided with an insertion stage 140 facing the developing section 24 of the developing and fixing device 28. Further, as shown in FIG. 2, on the drawing device 20 side of the insertion stage 140, a take-out claw 144 provided on the air cylinder 142 is arranged.

The transport stage 138 on which the printing plate 12 is mounted
Is moved to above the insertion stage 140, the air cylinder 142 operates and the take-out claw 144 protrudes. By moving the transport stage 138 to the standby position on the drawing device 20 side in this state, the printing plate 12 is moved to the transport stage 13.
8 and is placed on the insertion stage 140.

As shown in FIG. 3, the insertion stage 140
When the printing plate 12 is placed, the printing plate 12 is sent out at an inclination such that the developing unit 24 side faces downward. Thus, the printing plate 12 is inserted into the developing unit 24 at an angle corresponding to the inclination when the printing plate 12 is transported by the developing unit 24.

As described above, in the plate supply / discharge device 16 and the drawing device 20, the photosensitive layer of the printing plate 12 is charged and exposed without bringing the photosensitive layer into contact with the suction cup or the like, and is sent to the developing unit 24.

By the way, as shown in FIG.
Reference numeral 2 denotes a substantially rectangular flat plate which is larger than the printing plate 12 on which the exposure processing is performed. The drawing platen 22 includes the printing plate 12
Are provided with a plurality of pin rollers 146 and a pusher 148 facing the periphery of.

The pin roller 146 is capable of appearing and retracting on the surface of the drawing platen 22, and the pusher 148 is
The inside of the notch 150 formed so as to reach the periphery of the printing plate 12 from the periphery of the exposure platen 22 is movable. That is, the printing plate 12 placed on the drawing surface plate 22
Is positioned on the exposure platen 22 by being pressed toward the pin roller 146 by a pusher 148 that moves in the cut 150 so that an image is recorded at an appropriate position.

On the other hand, cuts 152 are formed on the drawing surface plate 22 at positions facing the claw portions 134 provided on the take-out unit 132, respectively. This cut 152
Is formed so as to reach from the periphery of the drawing surface plate 22 to a lower portion of the periphery of the printing plate 12 positioned on the drawing surface plate 22.

Thus, the printing plate 12 on the drawing platen 22 is
When taking out, the claw portion 134 of the take-out unit 132
Is lowered, each of the plurality of claw portions 134 enters the cut 152. In this state, by supporting the printing plate 12 by the claw portion 134, the claw portion 134 is moved within the cutout 152 so that the leading end reaches below the peripheral portion of the printing plate 12.

As described above, the printing plate 1 is placed on the exposure platen 22.
A number of cuts 150 and 152 (hereinafter, collectively referred to as “cuts 154”) are formed facing the peripheral edge portion 2.

On the other hand, as shown in FIG.
Is formed by a wire 156 arranged in a direction perpendicular to the moving direction of the printing plate 12 and a shield case 158 that covers the wire 156 in a state where the surface facing the printing plate 12 is open.

The drawing apparatus 20 is provided with a constant current power supply 160, and the power of the constant current power supply 160
30 wires 156. As a result, the charger 130 applies a predetermined high voltage to the wire 156 to generate corona discharge.

Further, the drawing base 22 and the constant current power supply 160 that are placed in contact with the support of the printing plate 12 are grounded, so that the drawing base 22 on which the printing plate 12 is mounted is charged. When passing through the position facing 130, the charges generated by the corona discharge are radiated toward the drawing surface plate 22, and the charging current flows out of the drawing surface plate 22. At this time, the printing plate 12 is charged according to the charging current.

The shield case 158 is connected to a ground line. When a corona discharge occurs, a shield current Is flows from the shield case 158 to the protection current power supply 160 via the ground line. When the drawing surface plate 22 reaches the position facing the charger 130, discharge from the charger 130 to the drawing surface plate 22 occurs, and the charging current Ic flows from the drawing surface plate 22 to the constant current power supply 160. Constant current power supply 160
Controls the total current (Is + Ic) of the shield current Is and the charging current Ic at this time to be constant (shield ground current control).

That is, the constant current power supply 160 is connected to the charger 1
By supplying a constant corona current Ik to the 30 wires 156, a predetermined high voltage is applied to the wires 156,
A corona discharge is generated in the wire 156. When the charge generated by this corona discharge reaches the shield case 158, the constant current power supply 1
60, the shield current Is flows. Also, the drawing surface plate 22
Reaches a position facing the charger 130, the charge generated by the corona discharge reaches the drawing surface plate 22, and the charging current Ic flows from the drawing surface plate 22 to the constant current power supply 160.
At this time, the constant current power supply 160 controls the corona current Ik so that Ik = Is + Ic.

It should be noted that the shield ground current control by the constant current power supply 160 can employ a conventionally known method, and a detailed description thereof will be omitted in the present embodiment.

The discharge of electric charge from the charger 130 toward the printing plate 12 on the drawing surface plate 22 is increased when the tip of the drawing surface plate 22 reaches the vicinity of the charger 130 and the ground surface approaches, and When the rear end of the board 22 passes through the position facing the charger 130 and the grounding surface is separated from the charger 130, the distance decreases.

On the other hand, a plurality of cuts 154 reaching the periphery of the printing plate 12 are formed on the drawing surface plate 22 at the end in the moving direction.
Are opened near the peripheral edge of the printing plate 12, and the contact surface is reduced.

Since the charging current Ic does not flow between the drawing surface plate 22 and the charger 130 unless the drawing surface plate 22 faces the charger 130, the constant current power supply 160 increases the corona current Ik. Increase the voltage on wire 156. Further, when the drawing surface plate 22 reaches the charger 130, the charging current Ic flows, and the charging current Ic changes in order for the constant current power supply 160 to control the corona current Ik so as to suppress the charging current Ic. .

Therefore, if the opening formed by the cut 154 formed at the end of the drawing platen 22 in the moving direction is wide, the charging current Ic changes rapidly near the end of the printing plate 12 along the moving direction. Thus, the potential at the end of the printing plate 12 increases.

Here, in the drawing surface plate 22 applied to the present embodiment, one or a plurality of cuts 154 are formed dispersedly at the end along the moving direction, and the drawing surface plate 2 is formed.
The ratio of the sum of the opening widths of the cuts 154 to the width dimension, which is a dimension along the direction orthogonal to the movement direction of No. 2, is 75% or less.

That is, as shown in FIGS. 6 (A), 6 (B) and 6 (C), cuts 154 are formed at one or a plurality of positions along the width direction of the drawing platen 22 having the width dimension W _D. when forming the, the width W _d of the opening of each notch _{154, W 1, W 2,} W 3, when a., the sum W _S of the opening width of the cut 154, W _S = W ₁ + W ₂ + W ₃ + W ₄ +..., And the aperture ratio Q is as follows: Q = (W _S / W _D ) × 100 (%) 6A, 6B, and 6C.
In the figure, the arrow indicates the moving direction of the drawing surface plate 22. 6A shows an example in which the cuts 154 are formed at six positions along the width direction of the drawing surface plate 22, and FIG. 6B shows one position at the center of the drawing surface plate 22 in the width direction. Cut 154
6C shows an example in which the notch 164 is formed as a notch 154 on both sides in the width direction of the drawing surface plate 22. FIG.

The drawing surface plate 22 limits the opening width Wd of the cut 154 so that the opening ratio Q is 75% or less (Q ≦ 75%). Accordingly, the charging current Ic is stabilized near both ends in the moving direction of the printing plate 12, and the charging current Ic changes abruptly, so that the potential increases like a spike near the end of the printing plate 12. Is prevented.

The operation of the present embodiment will be described below.

In the plate making system 10, when the start of the plate making operation is instructed, the skid 14 loaded in the plate
, The uppermost printing plate 12 is taken out and supplied to the drawing device 20. That is, in the plate supply / discharge device 16, the drawing device 20
When the printing plate 12 is requested from the
02, removes the printing plate 12 from the skid 14,
The printing plate 12 is drawn by the drawing apparatus 2 by the reverse transport unit 104, the lift table 112, the horizontal transport unit 114, and the like.
0 and is placed on the drawing surface plate 22.

In the drawing device 20, the printing plate 12 placed on the drawing platen 22 is moved by the pin rollers 146 and the pushers 14.
When the positioning is performed by 8, the photosensitive layer of the printing plate 12 is charged by the charger 130 while being moved toward the exposure unit 18. Thereafter, when the printing plate 12 is pulled out from below, the exposure unit 18 scans and exposes the printing plate 12 to form an electrostatic latent image.

When the printing plate 12 on which the electrostatic latent image has been formed is taken out of the drawing platen 22 by the take-out unit 132, it is carried by the carrying stage 138, sent out from the insertion stage 140 to the developing section 24, and developed and fixed. ,
Elution, drying, punching and plate bending are performed.

The charging device 130 provided in the drawing device 20 generates a corona discharge when the corona current Ik is supplied from the constant current power supply 160, and the moving table 122 moves to draw the image on the printing plate 12. As the board 22 passes below, the charges generated by the corona discharge are released toward the printing plate 12. Thereby, the photosensitive layer of the printing plate 12 is charged.

At this time, the constant current power supply 160 can uniformly charge the photosensitive layer of the printing plate 12 by controlling, for example, the sum of the charging current Ic and the shield current Is to be constant. That is, by making the charging current Ic flowing according to the charge generated in the photosensitive layer of the printing plate 12 by charging constant, the entire surface of the photosensitive layer has the same potential.

On the other hand, the drawing platen 22 on which the charged printing plate 12 is placed and moved is provided with a notch 152 into which the claw portion 134 of the take-out unit 132 enters at an end in the moving direction, and a positioning of the printing plate 12. Is formed near the edge of the printing plate 12 by changing the pusher 148 to move the pusher 148, so that the width (grounding surface) facing the charger 130 changes. Thereby, the printing plate 1
The charging current Ic changes near the end of No. 2 and the potential of the printing plate 12 to be charged easily changes.

Here, in the drawing surface plate 22, a plurality of cuts 154 are formed dispersedly at the ends along the moving direction, and the opening ratio Q of the ends of the drawing surface plate 22 by the cuts 154 is 75%. It is to be as follows. This suppresses an increase in the potential of the end of the printing plate 12 in the moving direction, and the entire surface of the printing plate 12 is charged substantially uniformly.

Table 1 shows that when a notch 154 reaching the peripheral edge of the printing plate 12 is formed at the end of the drawing platen 22 along the moving direction, the notch 154 from one end along the moving direction of the printing plate 12 is formed. The change of the surface potential for each distance is shown. In addition,
The measurement of this potential is performed by setting the moving speed v of the printing plate 12 to 5 m / mi.
n, the width dimension W _D of the drawing platen 22 was set to 1200 mm, and the printing plate 12 was positively charged. The potential difference with respect to the reference potential at the center and both ends along the moving direction on the printing plate 12 was measured. Is shown.

[0083]

[Table 1]

As shown in Table 1, when the cuts 154 are formed at the ends of the printing plate 12 in the moving direction along the width direction, a potential difference is not observed until the aperture ratio Q reaches 75%. However, when the aperture ratio Q becomes 100%, a potential difference occurs not only at both ends but also at the center. That is, when the aperture ratio Q exceeds 75%, a potential difference occurs between the printing plate 12 and the reference potential. If this potential difference is partial, it becomes a potential projecting from the surroundings in a spike shape.

Such a partial increase in the potential causes damage to the photosensitive layer of the printing plate 12, causing black spots or the like to appear on the printing plate 12, for example, causing a printed matter to have a defective finish such as printing stains.

On the other hand, when the aperture ratio Q is 75% or less, the potential at the end of the printing plate 12 along the moving direction is substantially equal to the reference potential. That is, the cut 154
Are distributed along the width direction of the drawing platen 22, the aperture ratio Q is set to 75% or less, so that the printing plate 1
The entire photosensitive layer 2 can be charged so as to have a substantially uniform potential.

If the aperture ratio Q is 75% or less, not only when the cuts 154 are dispersed in the width direction of the drawing platen 22 as shown in FIG. As shown in the drawing, a notch 1
54 (162) or as shown in FIG. 6C, when the cuts 154 (164) are formed at two places at both ends in the width direction of the drawing surface plate 22, It is possible to prevent a spike-like increase in potential at the end along the moving direction.

Therefore, when the notch 154 is formed in the drawing platen 22 on which the printing plate 12 is placed and moved, the printing plate 12 can be uniformly charged by setting the aperture ratio Q to 75% or less. Thus, it is possible to reliably prevent the photosensitive layer of the printing plate 12 from being damaged by the potential difference generated at the time of charging, thereby impairing the finish of the printed matter.

Note that a constant current power supply 160 may be provided with a limiter in order to suppress a sudden change in the charging current Ic. By setting the setting value of the limiter to be slightly higher than the working voltage, it is possible to suppress the occurrence of a spike-like potential increase in the charged potential of the printing plate 12. In addition, since the potential that rises in a spike shape changes according to the set value of the limiter, it is more preferable to appropriately set the set value based on the aperture ratio Q.

On the other hand, in the above description, the opening ratio Q based on the opening width W _d of the cut 154 with respect to the width dimension W _D of the drawing surface plate 22 is described.
However, the cut depth of the cut 154 along the moving direction of the drawing surface plate 22 also affects the potential when the printing plate 12 is charged.

Since the notch 154 has a depth reaching the peripheral edge of the printing plate 12, the distance between the end of the drawing platen 22 in the moving direction and the end of the printing plate 12 is at least the notch 154. And depth. That is, as shown in FIG. 7, when the distance from the end along the moving direction of the drawing surface plate 22 to the end of the printing plate 12 is a distance Y (mm),
Cutting depth D _d of the cut 154 is made slightly larger than the distance Y (Dd ≧ Y).

Here, when the plurality of cuts 154 are formed along the width direction of the drawing surface plate 22 so as to be dispersed so that the aperture ratio Q becomes 75% (see FIG. 7), FIG. 9 shows a measurement result of a potential difference with respect to the reference potential of the end of the printing plate 12 with respect to the distance Y when the distance Y of the end along the moving direction of the printing plate 12 is changed.

[0093]

[Table 2]

As shown in Table 2, when the edge of the printing plate 12 and the edge of the drawing surface plate 22 substantially coincide, the distance Y = 0 mm. In this case, the highest potential difference occurs at the end of the printing plate 12 along the moving direction. That is, the potential rises in a spike shape at the end of the printing plate 12 along the moving direction of the drawing surface plate 22.

On the other hand, the distance Y between the edge of the drawing platen 22 and the edge of the printing plate 12 along the direction of movement of the drawing platen 22.
Becomes larger, and the peripheral portion of the printing plate 12 moves away from the peripheral portion of the drawing surface plate 22, whereby the potential difference generated at the end of the printing plate 12 gradually decreases.

If such a potential difference is less than 5 V,
If the photosensitive layer of the printing plate 12 is not damaged, the electrostatic latent image formed on the printing plate 12 by exposure is not damaged, and there is no practical problem.
From this, the distance Y between the end of the drawing platen 22 and the end of the printing plate 12 along the moving direction of the drawing platen 22 during charging is set to 15
mm or more (Y ≦ 15 mm).

The distance Y is set to 30 mm or more (Y ≦ 30 m
m), the printing plate 12 has the drawing surface plate 22
The distance Y between the end of the drawing platen 22 and the end of the printing plate 12 along the moving direction of the drawing base plate 22 is set to 30 mm or more because no potential difference occurs at the end portion along the moving direction of the printing plate 12. Is more preferable.

That is, when the printing plate 12 is charged, the position of the printing plate 12 on the drawing platen 22 is
2 from the end of the drawing surface plate 22 along the moving direction of the printing plate 1
The distance Y to the end of No. 2 is preferably at least 15 mm or more, more preferably 30 mm or more.

Thus, when the printing plate 12 is charged while moving the drawing platen 22 on which the printing plate 12 is placed,
A spike-like potential difference can be substantially prevented from being generated at the end of the printing plate 12 along the moving direction of the drawing surface plate 22 (printing plate 12), and damage to the photosensitive layer due to the spike-like potential difference can be prevented. Can be prevented.

Also, by using such a drawing surface plate 22, the plate making system 10 does not cause a potential difference on the printing plate 12 which may affect the electrostatic latent image as well as damage the photosensitive layer. The printed plate does not impair the finish of the printed matter. That is, the plate making system 10 can create a printing plate from which a high-quality printed matter can be obtained.

On the other hand, in this embodiment, when forming the cut 154, the aperture ratio Q is set to 75% or less. However, this aperture ratio Q is a predetermined value only when the printing plate 12 is charged. What is necessary is just the value (75%) or less. That is, a closing means for filling the cut 154 is provided on the drawing surface plate 22, and the cut 154 is formed by the closing means when the printing plate 12 is charged.
A predetermined aperture ratio Q may be secured by closing at least a part of.

FIG. 8 shows an example of the closing means provided on the drawing surface plate 22. In the notch 154 of the drawing surface plate 22, there is provided a closing plate 170 having a thickness that can ensure that the opening of the notch 154 is substantially closed when viewed from the charger 130.

[0103] A coil spring 172 is provided between the closing plate 170 and the moving table 122.
Is biased and held by the biasing force of the coil spring 172 such that the upper surface is substantially flush with the upper surface of the drawing surface plate 22. Further, the closing plate 170 is connected to the take-out unit 13.
When the second claw 134 is lowered and pressed, the claw 134 is pushed into the notch 154 against the urging force of the coil spring 172, the claw 134 enters the notch 154, and the leading end is located below the peripheral edge of the printing plate 12. So that it can be inserted into

With this configuration, the claw portion 134 of the take-out unit 132 is inserted below the peripheral edge of the printing plate 12, and the printing plate 1 can be inserted without touching the photosensitive surface of the printing plate 12.
2 can be taken out, and the claw portion 134 moves upward and separates from the closing plate 170, so that the cut 1
By closing the openings 54, the opening ratio Q can be reduced.
Thereby, the photosensitive layer of the printing plate 12 can be uniformly charged.

The closing means is not limited to this, and any structure can be used as long as it closes the opening of the cut 154 at least when the printing plate 12 is charged.

Further, in this embodiment described above, an example in which the printing plate 12 is charged by shield current control has been described. However, the charging method of the printing plate 12 is not limited to this. Printing plate 1 by method
2 may be charged.

As shown in FIG. 9, in the shield feedback current control system, the shield case 158 of the charger 130 is connected to the constant current power supply 160A. Thus, when corona discharge occurs, the constant current power supply 1
A shield feedback current Is flows through 60A. Constant current power supply 1
60A controls the shield return current Is to uniformly charge the photosensitive layer of the printing plate 12.

That is, the constant current power supply 160A supplies a predetermined corona current Ik to the wire 156 of the charger 130 to apply a predetermined high voltage to the wire 156 to generate corona discharge. When the charge generated by this corona discharge reaches the shield case 158,
A shield feedback current Is flows from the shield case 158 to the constant current power supply 160A. When the drawing surface plate 22 reaches a position facing the charger 130, a charging current Ic flows through the charger 130 and the drawing surface plate 22. At this time, Ik = I
c + Is.

Here, in order to uniformly charge the photosensitive layer of the printing plate 12, the charging current Ic needs to be constant.
The constant current power supply 160A used for shield feedback current control is:
The charging current Ic is made constant by controlling the shield feedback current Is. The constant current power supply 1
For controlling the shield feedback current Is at 60 A, a conventionally known method can be applied, and a detailed description is omitted in the present embodiment.

[0110] From the charger 130 to the drawing surface plate 22
The discharge of the electric charges toward the upper printing plate 12 is started when the leading end of the drawing surface plate 22 reaches the vicinity of the charger 130 and the ground surface approaches, and the rear end of the drawing surface plate 22 faces the charger 130. It stops when it passes the position and the tread separates.

When the drawing surface plate 22 faces the charger 130, a charging current Ic flows between the drawing surface plate 22 and the charger 130. At this time, since the potential of the wire 156 decreases, the corona current Ik increases so as to suppress the decrease in the potential, so that the charging current Ic increases.

On the other hand, since the notch 154 is formed in the drawing platen 22, if the drawing platen 22 is opened near the periphery of the printing plate 12, the charging current Ic near the end of the printing plate 12. Increases, the potential at the end of the printing plate 12 increases.

Also in this case, by setting the opening ratio Q of the drawing surface plate 22 to 75% or less, the charging current Ic rapidly increases near the edge of the printing plate 12, and this charging current Ic
Increase in the potential of the edge of the printing plate 12 can be prevented.

The distance Y between the edge of the printing platen 22 and the edge of the printing plate 12 along the moving direction of the writing platen 22 at this time is preferably 15 mm or more, more preferably 30 mm or more. Accordingly, it is possible to suppress the occurrence of a spike-like potential increase at the end of the drawing surface plate 22 along the moving direction.

As a result, it is possible to prevent the photosensitive layer from being damaged by the potential difference generated on the printing plate 12, and to form an image on the printing plate 12 with a high finishing quality of the printed matter.

Note that the present embodiment described above does not limit the configuration of the present invention. In the present embodiment,
Although the plate making system 10 which forms an electrostatic latent image on the printing plate 12 taken out from the skid 14 and then performs development, fixing, elution, drying, punching and plate bending processing has been described as an example, the present invention is directed to shield grounding. Various types of current control methods, such as a current control method and a shield feedback current control method, are used to charge a printing plate by moving the photoconductor such as a printing plate relative to a charger for charging the printing plate. It can be applied to board and plate making systems.

[0117]

As described above, according to the present invention, when the photoconductor is charged by placing the photoconductor and moving relative to the charger, the end of the end in the relative movement direction is charged. By limiting the aperture ratio along the direction perpendicular to the moving direction to 75% or less, the photoconductor can be uniformly charged.

Further, in the plate making system of the present invention, a potential difference is generated at the time of charging, thereby preventing damage to the photosensitive layer, enabling formation of an appropriate electrostatic latent image, and impairing the finished quality of printed matter. An excellent effect of being able to surely prevent is obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a plate making system applied to the present embodiment.

FIG. 2 is a schematic configuration diagram of a plate supply / discharge device and a drawing device as viewed from one end side of a printing plate in a longitudinal direction.

FIG. 3 is a schematic configuration diagram of the plate supply / discharge device as viewed from one end side in the width direction of the printing plate.

FIG. 4 is a perspective view of a main part showing a schematic configuration of a drawing apparatus.

FIG. 5 is a schematic configuration diagram illustrating a charging mechanism of a printing plate.

FIGS. 6A to 6C are schematic diagrams showing examples of forming cuts at the ends of the drawing surface plate in the moving direction, respectively.
Shows an example in which a plurality of cuts are formed in a distributed manner along the width direction of the drawing surface plate, (B) shows an example in which cuts are formed in the center portion in the width direction of the drawing surface plate, and (C) shows the drawing. An example is shown in which cuts are formed at both ends in the width direction of the surface plate.

FIG. 7 is a schematic diagram showing a relative position between an end of a drawing surface plate in which a notch is formed in a moving direction and a printing plate 12;

FIG. 8 is a schematic diagram illustrating an example of a closing unit that lowers the aperture ratio of a drawing surface plate.

FIG. 9 is a schematic configuration diagram showing a printing plate charging mechanism based on a shield feedback current method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Plate-making system 12 Printing plate (photoconductor) 18 Exposure unit 20 Drawing device 22 Drawing platen (flat plate) 122 Moving stand 130 Charger 132 Extraction unit 134 Claw 148 Pusher 154 (150, 152, 162, 164) Cut 156 Wire 158 Shield case 160, 160 A Constant current power supply 170 Closing plate (closing means) 172 Coil spring (closing means)

Claims (4)

[Claims] A discharge wire disposed in a shield having an open surface, wherein the discharge wire is used to face a charger controlled by a current supplied from a high voltage power supply for discharge;
A charging platen for placing a plate-shaped photoconductor on a flat upper surface, and charging by discharging from the wire when the photoconductor passes a position facing the wire, wherein the wire is When forming a notch reaching the edge of the photoconductor at the end of the plate along the direction of relative movement with respect to the direction of movement of the plate relative to the board dimension along a direction orthogonal to the direction of relative movement. The opening ratio, which is the ratio of the total opening width of the cuts along the direction perpendicular to the opening, is 75%.
A charging surface plate characterized by the following. 2. A closing means for closing a part of an opening formed on an upper surface by the cut so that the total of the opening widths is not more than a predetermined value at least when the photoconductor is charged. The surface plate for charging according to claim 1. 3. The method according to claim 1, wherein a distance between an end of the flat plate and an end of the photoconductor along the relative movement direction is 15 mm or more, more preferably 30 mm or more. Surface plate for charging described in 1. 4. A plate-making system for forming a printing plate by forming an image on a printing plate using a photoconductor by charging exposure, wherein the image is subjected to image exposure after the printing plate is charged. A plate making system, comprising: an exposure unit provided with the drawing surface plate according to claim 1.